David C. Povey

Development of new technetium cores containing technetium—nitrogen multiple bonds. Synthesis and characterization of some diazenido-, hydrazido- and imido- complexes of technetium

Abstract The syntheses of several novel diazenido-, hydrazido- and imido- complexes of technetium are described. These precursors which contain technetium—nitrogen multiple bonds are derived directly from the appropriate organohydrazine or amine in good yield. Some of the chemistry has been extended to the metastable isotope 99mTc (γ, t 1 2 = 6 h) in highly dilute aqueous media to give single species in high radiochemical purity. These preparations are applicable to the synthesis of new technetium radiopharmaceuticals and should provide for the development of a whole new range of technetium-based diagnostic agents in nuclear medicine.

The preparation and substitution chemistry of the cationic bis(hydrazido(2−))rhenium(VII) complex [ReCl2(NNMePh)2(PPh3)][BPh4]. The crystal and molecular structures of [Re(NNMePh)2(S2CNMe2)2][BPh4] and [ReOCl(NNMePh)(PPh3)2][PF6]2

Abstract Reaction of [ReOCl3(PPh3)2] with MePhNNH2 in boiling methanol gives the orange five-coordinate bis(hydrazido) cation [ReCl2(NNMePh)2(PPh3)][BPh4] (1). Attempted recrystallization of 1 as its [PF6]− salt led unexpectedly to the brown crystalline oxo-hydrazido dication [ReOCl(NNMePh)(PPh3)2][PF6]2 (2). The structure of 2 was determined as five-coordinate with the oxo- and hydrazido-moieties in the equatorial plane of a trigonal bipyramid, and with the mutually trans-phosphine ligands occupying the axial sites. Complex 1 is a versatile starting material and reacts with the sodium dithiocarbamates (NaS2CNR2, R = Me and Et) to give the red-crystalline bis(hydrazido)-bis-(dithio-carbamato) cations [Re(NNMePh)2(S2CNR2)2][BPh4] [R = Me (3) and R = Et (4)]. The structure of 3 was determined as pseudo-octahedral with linear, mutually cis-NNMePh groups and cis-chelating dithiocarbamato ligands. Reaction of 1 with the sterically hindered thiol 2,6-dichlorobenzene thiol (DCTH) gives the orange cationic bis(hydrazido)-bis(thiolato) complex [Re(NNMePh)2(DCT)2(PPh3)][BPh4] (5). Reaction of the imido precursor [ReCl3(NPh)(PPh3)2] with excess MePhNNH2 gives the yellow imido-hydrazido cation [ReCl2(NPh)(NNMePh)(PPh3)][BPh4] (6). Complexes 1, 2 and 6 contain the formally isoelectronic cores [Re(NNR2)2]3+, [ReO(NNR2)]3+ and [Re(NPh)(NNR2)]3+.

Preparation, spectroscopic studies and structure of bis(triorganostannyl) esters of substituted aliphatic dicarboxylic acids

Bis(triorganostannyl) esters of phenylmaleic acid, citraconic acid, maleic acid, phenylsuccinic acid, methylsuccinic acid and succinic acid, R3SnO2CCR1: CHCO2SnR3 (R  Bu, Ph, Cy; R1  Ph, Me, H) and R3SnO2CCHR1·CH2CO2SnR3 (R  Bu, Ph; R1  Ph and R  Bu, Ph, Cy; R1  Me, H), have been prepared from R3SnOH or (BU3Sn)2O and the dicarboxylic acid or its anhydride. The structures of these compounds in the solid state are discussed with reference to their IR and Mossbauer spectra. The crystal structures of the bis(triphenylstannyl) esters of phenylmaleic acid and citraconic acid have been determined by single crystal X-ray diffraction. In the first diester, both tin atoms are occupying tetrahedral geometries, with no short intermolecular O ⋯ Sn contacts. In bis(triphenyltin) citraconate, the carboxylatotin attached to the substituted olefinic carbon is also four coordinate, but the second tin atom is five coordinate, due to intermolecular coordination by a carboxylate group from a neighbouring molecule [Sn ⋯ O 2.397(3) A], thereby giving rise to a polymeric chain structure. The tributylstannyl monoester of citraconic acid has been synthesized and its structure in solution assigned by 13C and 119Sn NMR spectroscopy and, in the solid state, by IR and Mossbauer spectroscopy.

Crystal and molecular structures of tetracarbonyl(3,3′-dimethyl-2,2′-bipyridine)-chromium(0) and -molybdenum(0) benzene solvates and the unsolvated tungsten(0) analogue

Abstract The crystal structures of the complexes of 3,3-dimethyl- 2,2′-bipyridine (L), cis-[W(CO)4L], cis-[MO(CO)4L] · C4H6 and cis-[Cr(CO)4L] · C6H6 have been determined by X-ray diffraction. These structures show that repulsion between the methyl groups is principally responsible for the geometric distortion in each complex. Within the ligand, L, the two pyridine rings suffer distortion, in opposite directions, to pseudo-boat conformations so as to optimize metal—nitrogen binding. The benzene solvent molecules are arranged in a layer structure alternating with units of the metal complex. The metal complex molecule is beyond van der Waals contact with the benzene solvent molecule in each case.

The crystal structures of 2-(2′-pyridyl)phenyltellurium(II) bromide and of the inclusion compound bis[2-(2′-pyridyl)phenyltellurium(II) chloride]·p-ethoxyphenyl-mercury(II) chloride

Abstract In 2-(2′-pyridyl)phenyltellurium(II) bromide (1) the coordination about tellurium may be described as pseudo-trigonal bipyramidal wth bromine (TeBr = 2.707(11) A) and nitrogen (TeN) = 2.236(11) A) atoms occupying axial positions. The equatorial plane comprises a carbon atome (TeC = 2.111(6) A) and two lone pairs of electrons. There are no significant intermolecular interactions between the six independent molecules in the unit cell. Bis[2-2′-pyridyl)phenyltellurium(II) chloride]·p-ethoxy-phenylmercury(II) chloride (2) may be regarded as an “inclusion compound” obtained by replacement of two RTeX (X = Cl or Br) molecules by two p-ethoxyphenylmercury(II) chloride entities. There is approximately linear coordination about mercury (CHgCl = 179.2°(4), Hg-C = 2.044(14) and HgCl = 2.328(4) A) and 2-(2′-pyridyl)phenyltellurium(II) chloride, with a structure similar to that of (1) above (TeN = 2.2366(6), TeCl = 2.558(1), TeC = 2.080(25) A). There are no significant intermolecular contacts.

Facile synthesis of complexes of vanadium(II) and the crystal and molecular structures of hexaaquavanadium(II) trifluoromethylsulphonate

Abstract The new vanadium(II) salt [V(H2O)6](CF3SO3)2 was crystallised from solutions obtained by dissolving metallic vanadium in aqueous trifluoromethylsulphonic acid. The cations in this complex are regular octahedra (VO distance=2.119(1) A) and are extensively hydrogen-bonded to the anions throughout the lattice. The salt is soluble in several organic solvents and should be a useful starting material in the preparation of vanadium(II) complexes. Thus [V(ethylenediamine)3](CF3SO3)2 has been prepared by the addition of ethylenediamine to a solution of [V(H2O)6](CF3SO3)2 in ethanol. The preparation of [VCl2(H2O)4], [V(H2O)6]Br2 and [V(H2O)6](BF4)2 from vanadium and the appropriate aqueous acid has been confirmed.

Synthesis and X-ray crystal structure of a mercury(II)-telluroamine complex. Monodentate behaviour by a potentially bidentate hybrid telluride ligand, 1-(NMe2)-2-(TeC6H4-4-OEt)-4-MeC6H3

Abstract The telluroamines 1-(NMe2)-2-(TeAr)-4-MeC6H3 (1) (Ar = 4-MeOC6H4 or 4-EtOC6H4) react with mercury(II) halides forming adducts of composition HgX2 · 1 (X = Cl or Br). The IR, far-IR (up to 50 cm−1), 1H and 13C NMR spectra of the mercury(II) complexes indicate that the ligands (1) behave as monodentate donors, coordinating through tellurium only. The complexes seem to be dimers of the composition [1 · XHg(μ-X)2HgX · 1]. The crystal structure of the adduct obtained from mercury(II) bromide has been determined. It reveals that the NMe2 group does not coordinate with mercury(II) and the complex is a dimer in which two somewhat asymmetrical bromine bridges are present between the mercury atoms. The coordination environment of each mercury is almost tetrahedral [91.25(3)–118.40(4)°]. The HgBr bridging bond lengths are 2.755(1) and 2.710(1) A.

Synthesis and characterization of some novel pentagonal bipyramidal 2,6-diacetylpyridine bis(benzoylhydrazone) (DAPBH2) complexes of Rhenium(III) and molybdenum crystal and molecular structure of [ReCl(DAPB)(PPh3)]. An investigation of the Mössbauer spectroscopy of [FeIICl2(DAPBH2)]·H2O and [FeIIICl(DAP-Me-B)(H2O)] ☆

Abstract Reaction of [ReCl3(MeCN)(PPh3)2] with the planar pentadentate diacetylpyridinebis(benzoylhydrazone) ligands DAPBH2 and DAP-Me-BH2 and triethylamine in isopropanol under reflux gave the dark brown seven-coordinate complexes [ReCl(L)PPh3], containing the doubly deprotonated pentadentate ligand [L = DAPB(2−)(1); L = DAP-Me-B(2−) (2)]. Complex 1 has been characterized by crystallography. The central rhenium atom in 1 is seven-coordinate, with pentagonal bipyramidal geometry with the axial positions being occupied by the chloride ion and the triphenylphosphine ligand. The DAPB coordinates in a pentadentate manner in the equatorial plane of the complex and the five donor atoms of the doubly deprotonated DAPB(2−) ligand form an approximately planar pentagon. The rhenium atom is slightly displaced out of the ligand plane towards the phosphorus atom. Reaction of 2 with Ag[BF4] in CH2Cl2 at room temperature gave a black complex of stoichiometry [Re(DAP-Me-B)(PPh3)][BF4] (3). Reaction of [MoCl4(MeCN)2] with DAP-Me-BH2 and Et3N in dry CH2Cl2 under reflux gave deep green [MoCl2(DAP-MeB2)] (4), formulated as a seven-coordinate molybdenum(II) complex containing the doubly deprotonated pentadenate DAP-MeBH2 ligand in the equatorial plane of the complex. The Mossbauer spectra of the complexes [FeCl2(DAPBH2)]·H2O (5) and [FeCl(DAPMe-B)(H2O)] (6) were investigated as a function of temperature. The spectrum of 5 was consistent with high-spin seven-coordinate iron(II) and 6 was shown to contain two distinct iron(III) sites; possible structures are discussed.

Synthesis and structural studies of complexes of vanadium(II) and vanadium(III) halides with tertiary phosphines

Abstract The vanadium(II) halides [VCl2(H2O)4] and [V(H2O)6]Br2, prepared from the metal and the appropriate acid, combine with 1,2-bis(dimethylphosphino)ethane (dmpe) and 1,2-bis(diethylphosphino)ethane (depe) in methanol to give [VX2(dmpe)2] and [VX2(depe)2] (XCl or Br). The iodo complexes were obtained from [V(MeOH)6]I2, although [VI2(depe)2] was not pure. The complexes [VX2(dppe)2]·2thf (XCl or Br; dppe=1,2- bis(diphenylphosphino)ethane) could not be isolated from methanol, but were obtained from tetrahydrofuran (thf). All are typical vanadium(II) complexes, and [VCl2(depe)2] and [VCl2(dppe)2]·2thf have trans structures. The VCl bond distances, 2.445(2) and 2.420(1) A, respectively, are similar to that in the known complex [VCl2(dmpe)2], but the VP bond distances are longer by approximately 0.06 A and the PVP angles are smaller by c. 3°, possibly due to the steric crowding of the more heavily substituted depe and dppe ligands in the equatorial plane. Some new complexes [VX3(PR3)n] (XCl or Br, PR3=monotertiary phosphine, n=2 or 3) were also prepared from [VX3(thf)3].

The Chemistry of the trivalent actinoids. Part 7 [1]. Crystal structure analysis of [NH4]U[SO4]2·4H2O and comments on the structure of U2[SO4]3·9H2O

Abstract The crystal structure of an hydrated uranium(III) compound has been determined for the first time. Crystals of [NH4]U[So4]2·4H2O are monoclinic with a = 6.7065(2), b = 19.0328(6), c = 8.8305(3) A, β = 97.337(10°, z = 4 and space group P21/c. The structure was solved by the heavy-atom method from Cu-Kα diffractometer data, and refined by full-matrix least aquares to R = 0.096 for 1647 observed reflections. The compounds is isostructural with [NH4]M[SO4]2·4H2O (M = LaTb, except Pm). Each uranium atom is coordinated to nine oxygen atoms; six of them are contributed by four sulphate groups and the remaining three are from water molecules. The uranium-oxygen bond lengths were 2.37-2.60 A (to sulphate ion) and 2.47-2.56 A (to water). Each asymmetric unit contains a non-coordinated water molecule. The X-ray powder diffraction photograph of a substance previously reported as U2[So4]3·8H2O and that of La2[SO4]3·8H2O showed that compounds are isomorphous, with space group P63/m. Thus, the stoichiometry U2[So4]3·9H2O is more likely with nine/twelve-coordination found for the lanthanoid(III) sulphate octahydrates and Am2[SO4]3·8H2O. By comparing the diffuse reflectance electronic spectra of the title compounds with those of various uranium(II) solutions, it is confirmed that both water and sulphate ion have similar nephelazuxetic factors.